ZIP Code Density

I've been playing with some neat data from the 2010 Census, and in honor of Memorial Day I thought this was a super fun plot to show. The actual post that I'm working on related to this will probably take a long time to complete, as it requires I gather a ton of data...

I'm using the "CubeHelix" color scheme (shameless promotion: I wrote the first version for IDL). This scheme is great because it de-saturates from color to black/white while correctly preserving brightness. It can be rainbow colors too, not just monotone like above.

For example, here is the same figure, but with the color turned off (using Apple's Preview app). Great for making figures that look good both online (where color printing is free) and in black/white print (e.g. ApJ charges $350 per color figure, last I checked)